The present invention relates to a rotary turning attachment with at least two tools, comprising a cylindrical body designed to be mounted on the spindle of a machine tool, at least two slides designed to move radially with respect to the axis of rotation of the body, each of the slides being secured to a removable tool holder.
The present invention relates more particularly to cylindrical turning attachments equipped with interchangeable tip holders for standard ISO tips. These attachments are intended for the spindles of transfer machines and special machines. For many years, this type of machine has been suited only to the mass production of parts that can be machined relatively easily. The increasingly stringent demands for precision and productivity, the constant efforts to reduce production costs and the considerable advances made in cutting tips means that it can now be envisaged for these machines to be used for moderate or even short production runs, and materials which are more difficult to machine. Production changes are far more frequent. It is thus necessary to drastically reduce the unproductive time by reducing the setting time, which is still relatively lengthy. Often, the machining of a difficult material and tight tolerances entail frequent interventions to make microadjustments or change the cutting tools or tips.
Most manufacturers of transfer machines have their own system of tooling and the users have barely any choice and have to tolerate the inconveniences of this situation. Often too, the very restricted amount of space available limits the use of standardized conventional or quick-change tool holders.
There is a real need for improvement and rationalization; even though users are doing the best that they can, they are still, however, waiting for rational tooling that meets their needs.
The object of the present invention is to propose a very compact rotary turning attachment which is suited to customary and standardized machine-tool spindles. Thus, for example, in the case of the attachment set out according to the invention, the outside diameter is 42, 50, 63 or 83 mm with a working diameter between the cutting edges of the tips that can vary between 2 and 48 mm. Larger attachments are obviously also feasible.
The rotary attachment according to the invention is one wherein the cylindrical body comprises, on one plane face, one slideway per slide, formed in a recess running along a radius of said plane face and designed to allow the slide to move; at least two plates are attached removably to said face of the body, so as to hold the slides in the respective slideway in the direction of the axis of rotation of the turning attachment; said attachment comprises at least two housings, each running from the lateral surface of the cylindrical body inward, parallel to said slideway, said cylindrical housings being designed to take the micrometer screws each of which controls the individual movement of one slide; and said cylindrical housings each open into a housing of larger dimensions communicating with the corresponding slideway, the latter housing allowing a nut secured to a slide to be housed and moved therein, the threaded part of a micrometer screw being engaged in said nut.
The advantage of this turning attachment is that in spite of its small size, its relatively small volume is able to house means which allow the movement of the cutting tools to be set precisely.
According to one alternative form, when the need is there and depending on the diameter of the attachment, a concentric bore allows a cutting tool to be attached coaxially with a screw arranged radially in the body.
Upward of a certain size, a taper nut can be housed at the center and, in collaboration with a taper collet placed directly in the spindle of the machine on which the attachment is mounted, allows a tool to be attached coaxially using standardized double taper collet chucks (DIN 6499) or the like.
According to another alternative form, the slide is locked by the deformation of the plates using a binding screw acting on the part of the slide located in the slideway, the deformation being facilitated by an appropriate clearance in the face of the body under each semicircular plate. The plates may also be locally thinned in order to adapt their flexibility.
According to another alternative form, the micrometer screws controlling the movement of the slide are held in place by pins engaged in a groove near to the head of the corresponding screw.
According to another alternative form, the slides are designed also to allow axial adjustment of the tool supported by a tool holder.
As a preference, the slides are equipped with a toothed face facing axially so that interchangeable tool holders equipped with an oblong opening running axially and allowing the attachment member to pass can be attached thereto.
According to a preferred alternative form, the tool holder is equipped with an axial adjustment member which moves parallel to the direction of adjustment, pressing against a surface of the slide perpendicular to said direction of travel.
As a preference, the attachment member and the axial adjustment member are, on the one hand, an attachment screw and, on the other hand, a self-locking thrust screw incorporated into the tool holder.
It is obvious that a key or mutual nesting of the two flat faces of the slide and of the tool holder may just as easily constitute axial guidance for adjustment and positioning. However, to produce this short and rigid construction in a very tight space without reducing the ability of the slide and of the tool holders to withstand the cutting forces, the risks of vibration and centrifugal force at high speed, it has proved necessary to keep carefully sited ribs which keep the cross section of the two components high enough.
What is more, the axial adjustment thrust screw is incorporated into the tool holders at a suitable location so that by butting against the slide it contributes to the rigidity of the two elements assembled. Another special feature of this construction automatically allows the thrust screw to press firmly in the axial direction against the slide as the tool holders are clamped. Specifically, in an alternative form, the face of the tool holders on which the head of the attachment screw acts is inclined slightly so that by turning it to the right to lock it, the face of the head of the screw preferably acts on the side via which this generates a resulting force which also axially presses the tool holder against the slide via the axial adjustment thrust screw. This characteristic therefore additionally provides an increase in rigidity, an improvement in the precision of the axial adjustment while eliminating any risk of slight backward movement of the tool holder with respect to the slide while it is being locked by the transverse attachment screw. The latter can protrude beyond the slide and thus be fitted with an additional safety nut, depending on the dimensions of the attachment, of course.
These novel particular features of the construction of these attachments offer ease of adjustment and at the same time machining performance which are unique to attachments as compact as this with such a capability. Such attachments have a working capability of a maximum diameter of 48 mm for an attachment outside diameter of 83 or a capability of 22 mm diameter for an outside diameter of 52 mm, for example.